There is a need for methods for the use, storage or recovery of forms of energy which at present are under-utilised, or utilised inefficiently. Examples of such forms of energy are waste heat from industrial processes, heat from waste incineration, and solar energy in various forms, such as insolation, tidal energy, wind energy, ocean currents and hydrodynamic energy. Insolation energy conversion in particular is the subject of intensive research. Present methods of collection of solar energy mainly depend either on using the solar collector to heat water and generate steam which is then converted to rotary motive power, or on using solar radiation to produce electrical energy in solar cells. Other forms of waste heat energy are often utilised by heating water and generating steam. In such processes, major losses in the energy collection and conversion to steam are inherent. In addition, the energy collected and converted cannot be economically stored. Such a disadvantage is particularly acute in the collection of solar energy, because of the variability and unpredictability of the incidence of solar radiation.
The direct conversion of solar energy to electricity is at present only possible with relatively low efficiencies. Current methods of storing solar energy converted into electrical power are by use of electrical storage batteries but in most cases, known batteries are too expensive and inefficient to justify their widespread use.
A further shortcoming of present energy supply technologies results from the need for large scale commercial producers of electricity to install generating capacity substantially in excess of the average demand, because electricity generating plant must meet peaks of demand, which typically occur in the mornings and evenings and which are usually highest in winter, and because there previously existed no convenient and inexpensive method for storing electrical energy on a large scale.
Thus, there is a need for a method which provides for efficient conversion and/or storage of energy, particularly waste or low grade heat energy.
The unusual properties of graphite render it of surprising utility in the collection and storage of energy. The useful properties of graphite in this connection include: (a) its high thermal conductivity, (b) its high heat capacity, especially at elevated temperatures and (c) heat lost by radiation is relatively low when graphite is hot (except for long wavelength radiation).
Further, known methods for the utilisation of solar energy in its various forms are subject to inefficiencies, particularly, in the case of windmills or water turbines, at low air or water flow rates (such as in low winds, in the case of windmills.) Thus there is a need for an improved apparatus for generating electricity from a moving fluid, and for a an improved apparatus for more efficiently converting solar energy in the form of wind or water power into more directly usable heat energy.
Additionally, known methods for the collection of solar radiation using lenses or mirrors tend to be cumbersome and expensive owing to the need for sophisticated tracking equipment to permit the lens or mirror to be positioned at all times of the day and in all seasons so as to collect the sun's rays. There is therefore a need for an improved process for producing a lens which can simplify the collection of solar radiation.